How does the bacterial transcription-coupling repair factor promote adaptive mutagenesis in Campylobacter jejuni?

细菌转录偶联修复因子如何促进空肠弯曲杆菌的适应性诱变？

• 批准号: BB/I007172/1
• 负责人: Nigel Savery
• 金额: $ 20.78万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FI007172%2F1
• 关键词: How; does; bacterial; transcription; coupling

Campylobacter jejuni is a bacterium that causes food poisoning. Many animals that are raised for food production are colonised by C. jejuni, although this does not usually make the animals ill. However, when humans are infected (for example by infected chicken meat that has not been properly cooked) they can suffer from diarrhoea, and sometimes more serious illnesses. It is estimated that in developed countries like the UK about 1 in every 100 people suffer Campylobacter-related illness each year. This represents a large cost to the community in terms of lost working days, as well as discomfort for the individuals concerned. Most people recover from C. jejuni, infections without medical intervention, but when treatment is considered necessary the patients are often prescribed a class of antibiotics called Fluoroquinolones. Fluoroquinolones kill cells by inhibiting specific enzymes within the cell, but if bacteria change the sequence of the DNA that codes for these enzymes they can become resistant to the antibiotic. The increasing prevalence of antibiotic resistant bacteria is a growing problem for both human and animal health. When stressed, bacteria can sometimes change their physiology so that their DNA mutates more quickly than it would do normally. Although most of the mutations that occur will be detrimental to the cell, some (such as those that confer antibiotic resistance) will be beneficial. Because bacteria reproduce very quickly if one or two individuals acquire mutations that allow them to survive in a new environment they will rapidly grow into a substantial population of adapted bacteria. It has recently been discovered that C. jejuni can rapidly mutate to become Fluoroquinolone-resistant because when it encounters the antibiotic it makes more of a protein called Mfd. The same mechanism for increasing mutation frequency also seems to be used when C. jejuni is exposed to other antibiotics, and it may represent a universal strategy for helping C. jejuni to adapt to extreme changes in its environment. It is important to understand how this adaptive strategy works, not only so that we can understand how C. jejuni reacts to antibiotic treatment, but also so that we can understand how it might adapt to changes that we make in the environment that food-producing animals are reared in, or mutate to cause more serious disease. The finding that the Mfd protein increases the mutation rate is paradoxical, because the protein is best known as a DNA repair protein that prevents mutations arising in bacterial genomes. For several years we have been studying the Mfd protein in a model organism called Escherichia coli. We have gained a good understanding of this multi-functional protein, and we have identified many altered forms of the protein, each of which is specifically defective in a single function. The central aim of the work in this proposal is apply this knowledge to understand how overproduction of Mfd increases the rate of mutation in C. jejuni. We will identify which functions of Mfd, and which of the proteins that it cooperates with, are needed for the process, and we hope that the understanding that we gain will help microbiologists to control the rate of mutation of C. jejuni by developing strategies that avoid or interfere with the mutation-generating pathway.

空肠弯曲杆菌是一种引起食物中毒的细菌。许多饲养用于食品生产的动物都被C.空肠，虽然这通常不会使动物生病。然而，当人类被感染时（例如被未经适当烹饪的受感染鸡肉感染），他们可能会患腹泻，有时甚至会患上更严重的疾病。据估计，在像英国这样的发达国家，每年大约每100人中就有1人患有弯曲杆菌相关疾病。这意味着社区损失了大量工作日，有关个人也感到不适。大多数人从C中恢复过来。空肠炎，感染没有医疗干预，但当治疗被认为是必要的，病人往往是规定一类抗生素称为氟喹诺酮类。氟喹诺酮类药物通过抑制细胞内的特定酶来杀死细胞，但是如果细菌改变了编码这些酶的DNA序列，它们就会对抗生素产生抗药性。抗生素耐药性细菌的日益普遍是人类和动物健康的一个日益严重的问题。当受到压力时，细菌有时会改变它们的生理机能，使它们的DNA比正常情况下更快地突变。虽然大多数发生的突变对细胞是有害的，但有些突变（如赋予抗生素抗性的突变）将是有益的。因为细菌繁殖非常快，如果一个或两个个体获得突变，使它们能够在新的环境中生存，它们将迅速成长为适应细菌的大量群体。最近发现C.空肠可以迅速突变成为氟喹诺酮耐药，因为当它遇到抗生素时，它会产生更多的一种称为Mfd的蛋白质。当C.空肠暴露于其他抗生素，这可能是帮助C.空肠适应环境的极端变化。理解这种自适应策略是如何工作的是很重要的，这不仅是为了让我们能够理解C。空肠对抗生素治疗有反应，但也使我们能够了解它如何适应我们在食用动物饲养环境中所做的改变，或突变导致更严重的疾病。Mfd蛋白增加突变率的发现是自相矛盾的，因为该蛋白最为人所知的是防止细菌基因组突变的DNA修复蛋白。几年来，我们一直在研究一种名为大肠杆菌的模式生物中的Mfd蛋白。我们已经对这种多功能蛋白质有了很好的了解，并且我们已经鉴定了这种蛋白质的许多改变形式，其中每一种都在单一功能上有特定的缺陷。这项工作的中心目标是应用这些知识来了解Mfd的过度生产如何增加C中的突变率。空肠。我们将确定Mfd的哪些功能，以及它与哪些蛋白质合作，是这个过程所需要的，我们希望我们所获得的理解将有助于微生物学家控制C的突变率。空肠通过开发策略，避免或干扰突变产生途径。